1. Field of the Invention
The present invention generally relates to apparatus for assembling vehicle bodies, and more particularly, is directed to improvements in a vehicle body assembling apparatus which is provided in a vehicle body production line and operative to mount various parts on vehicle bodies conveyed thereinto after passing through a coating process.
2. Description of the Prior Art
There has been previously proposed a vehicle body assembling apparatus which is installed in a vehicle body production lne so as to be operative to detach doors from vehicle bodies conveyed into the apparatus after passing through a coating process and to mount various door parts and body parts on each of the doors detached from the vehicle bodies and each of the vehicle bodies without the doors, respectively, then to attach each of the doors provided fully with the door parts to the corresponding vehicle body provided fully with the body parts, as disclosed in, for example, the Japanese patent application published before examination with the publication No. 53/8884 on Jan. 26, 1978. In such an apparatus, the doors detached from the vehicle bodies are transported to a door assembly line through a door conveying device comprising a plurality of overhead conveying carriers and a plurality of door hangers each connected to the overhead conveying carrier, and the doors on each of which the door parts are mounted in the door assembly line are further transported to a door mounting station in the vehicle body production line, to which the vehicle bodies each provided fully with the body parts are conveyed.
In the case of the apparatus mentioned above, it is required that the time lapsed during a body parts mounting period from a process in which the door is detached from the vehicle body to an advanced process in which the vehicle body provided fully with the body parts is conveyed to the door mounting station is equal to the time lapsed during a door parts mounting period from the process in which the door is detached from the vehicle body to another advanced process in which the door provided fully with the door parts is conveyed through the door assembling line to the door mounting station. However, the number of the body parts mounted on the vehicle body without doors is much greater than the number of the door parts mounted on the door, and therefore, in fact, the time lapsed during the body parts mounting period is longer almost beyond comparison than the time lapsed during the door parts mounting period. Accordingly, in practice, the door conveying device is controlled to transport each of the doors at extremely slow speed or to carry each of the doors along a predetermined roundabout path to the door mounting station, in order to prolong the time lapsed during the door parts mounting period so as to be substantially proportionate to the time lapsed during the body parts mounting period.
For such a control for prolonging the time lapsed during the door parts mounting period, the door conveying device is required to have a large number of door hangers and consequently a housing structure supporting the door conveying device must necessarily be constructed firmly enough to support the device. This results in a problem that the expenses of facilities are considerably increased, and further in a disadvantage that the increase in the number of door hangers generates loud noises.